Tropical Storm Kiko Discussion Number 30
NWS National Hurricane Center Miami FL EP132019
200 PM PDT Thu Sep 19 2019
In terms of organization (and latitude) Kiko appears to have hit
rock bottom and may now be on its way back up (and north). After the
last advisory, Kiko briefly lost all of its central deep convection
and consisted of a low-level swirl of clouds. Since then,
convective activity has increased substantially and now a rain band
appears to be trying to wrap around the northern semicircle of the
tropical storm. ASCAT data around 1800 UTC showed max winds of only
35-40 kt, but given the improvement in the structure of Kiko since
that time, the initial intensity is conservatively lowered to 45 kt.
Aside from small adjustments due to the lower initial intensity,
little change was made to the intensity forecast. Most of the
guidance calls for at least slight strengthening, and the dynamical
models are still calling for Kiko to become a hurricane again. Dry
air is still the primary limiting factor, and if Kiko can ever
reform a well-defined inner-core, it could strengthen more quickly
than forecast. By the end of the forecast period, Kiko could
encounter an even drier environment and most of the guidance calls
for weakening.
Kiko is beginning to turn west-northwestward, and a turn toward the
northwest is expected soon. The tropical storm is still forecast to
move slowly westward on a wave-like path due to fluctuations in the
strength of a mid-level ridge to the north. The track guidance is in
particularly poor agreement on the speed Kiko will move west and by
day 5 the ECMWF and GFS are 750 mi apart. Although only minor
changes were made to the NHC forecast, which remains near the model
consensus, confidence in the track forecast is much lower than
usual.
Hurricane Kiko Discussion Number 11
NWS National Hurricane Center Miami FL EP132019
800 PM PDT Sat Sep 14 2019
Kiko has undergone a remarkable intensification over the past 24
hours. The initial intensity for this advisory is 100 kt, 55 kt
higher than last night's estimate at the same time. The hurricane
briefly developed a very clear eye earlier today, and although the
eye has become slightly obscured by an increase in eyewall
convection, it still has a very impressive satellite appearance.
The 100 kt intensity is based on a blend of recent subjective and
objective estimates that range from 90 to 105 kt.
There is no obvious reason why Kiko would stop strengthening in the
short term. The hurricane is clearly not being affected by any of
the dry air to its east, SSTs beneath the cyclone are warm, and the
shear is quite low. This should be the case for the next 36 h or
so, and Kiko is expected to at least maintain its current strength
through that period. Beyond that time, the intensity forecast is
quite complicated. Kiko will be moving nearly parallel to a strong
SST gradient. If the hurricane moves farther south than forecast,
it could maintain its strength for longer than indicated. But if it
moves farther north, it will likely weaken quickly. Kiko is also
forecast to slow down, and upwelling of colder water could also
become a factor in a few days, even if the hurricane stays on the
warm side of the SST gradient. The NHC forecast continues to show
gradual weakening beyond 36 h, but is on the high side of the
intensity guidance, most of which is tied to a forecast track north
of the latest NHC forecast.
The hurricane has slowed a little but is still moving west with a
motion of 270/8 kt. For the next couple of days a mid-level ridge
should keep Kiko moving generally westward at a similar forward
speed. Beyond that time, there is significant divergence between
the models. The GFS and regional hurricane models all show the
ridge weakening, allowing Kiko to turn northwestward. The ECMWF and
UKMET (as well as a clear majority of their ensembles) show no such
weakness forming and keep Kiko moving steadily westward through
mid-week. Unfortunately, no one solution appears superior at this
point, so the NHC forecast isn't fully following either group of
models. Instead it has been adjusted only modestly southward, and
remains close to the multi-model consensus. Needless to say,
confidence in the forecast is quite low.
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